Antenna G/T, Characteristic Impedance, Impedance Matching, losses & single & Double Stub Matching

Описание: This quantity is important because, the signal-to-noise ratio (SNR) at the input to a receiver is proportional to G/TA.
The ratio G/T can often be maximized by increasing the gain of the antenna, since this increases the numerator and usually minimizes reception of noise from hot sources at low elevation angles.
Higher gain requires a larger and more expensive antenna, and high gain may not be desirable for applications requiring omnidirectional coverage (e.g., cellular telephones or mobile data networks), so often a compromise must be made.
The transmission line, if not terminated with a matched load, occurs in losses.
These losses are many types such as attenuation loss, reflection loss, transmission loss, return loss, insertion loss, etc.
(1)Attenuation Loss
The loss that occurs due to the absorption of the signal in the transmission line is termed as Attenuation loss.
(2) Reflection Loss
The loss that occurs due to the reflection of the signal due to impedance mismatch of the transmission line is termed as Reflection loss.
(3)Transmission Loss
The loss that occurs while transmission through the transmission line is termed as Transmission loss.
(4) Return Loss
The measure of the power reflected by the transmission line is termed as Return loss.
(5) Insertion Loss
The loss that occurs due to the energy transfer using a transmission line compared to energy transfer without a transmission line is termed as Insertion loss.
At higher microwave frequencies, basically two stub matching techniques are employed.
(1) Single Stub Matching
(2) Double Stub Matching